Abstract:L band Radar and Electrical Radiosonde System (LRERS) had been employed widely ，but the detection accuracy of L band Radar was obtained only by check ing short distance static objects, which lacked related dynamic test. In order t o know the altimetry precision of LRERS, a new radiosonde with GPS function modu le was developed, In view of high precision GPS being generally acknowledge d in the world, 23 electrical radiosondes with GPS function model was set free w hich were traced by L band radar in Shanghai and Nanjing from the last ten days of May to the first ten days of June,2006. It is demonstrated from the analyzed result of 23 intercomparison data that As a wind-finding equipment, the height measuring error of L band radar is rather big because of the less ac c uracy of the horizontal calibration precision，the most system deviation is seve ral hectometers under the height of 100hPa. At the same time,it is found that t he error is systematic at a given station. However, if the radar level is adjust ed refer to the intercomparison result with GPS position data, the accuracy of t he height measurement may be improved in much more degree, which is less than 40 meters below 100hPa height. so it is feasible to use GPS position data as Calib ration reference method of L band Radar.